1. Field of the Invention
The invention relates to a system having at least one superconducting cable which has at least one superconducting conductor, and having a cryostat which surrounds the same and consists of two metallic tubes, an inner tube and an outer tube, which are arranged concentrically at a distance from one another, are corrugated transversely with respect to their longitudinal direction and between which vacuum insulation is arranged (EP 1 720 176 B1).
2. Description of Related Art
With modern technology, a super conducting cable has electrical conductors composed of a composite material, which contains ceramic material, which changes to the superconducting state at sufficiently low temperatures. The electrical direct-current resistance of a correspondingly constructed conductor is zero when adequate cooling is provided, provided that a specific current level is not exceeded. By way of example, suitable ceramic materials are YBCO (yttrium barium copper oxide) or BSCCO (bismuth strontium calcium copper oxide). By way of example, sufficiently low temperatures to change a material such as this to the superconducting state are between 67 K and 110 K. Suitable coolants are, for example, nitrogen, helium, neon and hydrogen, or mixtures of these substances.
DE 601 29 172 T2 discloses a current transport system having a superconducting cable with a cold dielectric, which is arranged in a cryostat which consists of two tubes, which are arranged concentrically with respect to one another and are separated from one another by vacuum insulation. The cable has a superconducting conductor which is fitted on a tubular support, a dielectric surrounding the same, and a superconducting return conductor which is fitted over the same. It is arranged in the cryostat leaving a free space for a coolant to pass through, which coolant can also be passed through the tubular support. A system such as this has relatively high electrical alternating-current losses, as a result of which a relatively thick insulating dielectric is required, because of the increased electrical field strength. The dimensions of the cable, and accordingly also those of the cryostat, are correspondingly large.
In the system according to the initially cited EP 1 720 176 B1, a superconducting cable with a corrugated profile is arranged in a cryostat, which consists of two metallic tubes which are arranged concentrically with respect to one another and are corrugated transversely with respect to their longitudinal direction. Vacuum insulation is located between the tubes. The corrugated profile of the cable is ensured by a network which is attached to the same at specific points. The aim in this case is to compensate for the contraction of the cable which occurs when it cools down. In this system, the cryostat also surrounds not only the cable but also a cavity for a coolant to pass through, thus resulting in the same defects as in the system according to DE 601 29 172 T2.